[LLVMbugs] [Bug 17373] New: wrong code (SIGFPE) at -O3 (affecting all clang versions on x86_64-linux-gnu and MacOS X)

[bugzilla-daemon at llvm.org]

http://llvm.org/bugs/show_bug.cgi?id=17373

            Bug ID: 17373
           Summary: wrong code (SIGFPE) at -O3 (affecting all clang
                    versions on x86_64-linux-gnu and MacOS X)
           Product: clang
           Version: trunk
          Hardware: PC
                OS: All
            Status: NEW
          Severity: normal
          Priority: P
         Component: LLVM Codegen
          Assignee: unassignedclangbugs at nondot.org
          Reporter: su at cs.ucdavis.edu
                CC: llvmbugs at cs.uiuc.edu
    Classification: Unclassified

The following code is miscompiled by the current clang trunk and older versions
on x86_64-linux-gnu at -O3 in both 32-bit and 64-bit modes.  

It also affects MacOS X. 

This may be caused by miscompiling the expression "b ? 1 : a / b". The
expression has undefined behavior, but the body of the inner loop isn't
executed. 


$ clang-trunk -v
clang version 3.4 (trunk 191356)
Target: x86_64-pc-linux-gnu
Thread model: posix
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.4
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.4.6
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.4.7
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.6
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.6.3
Selected GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.6
$ 
$ clang-trunk -O2 small.c; a.out
$ clang-trunk -O3 small.c; a.out
Floating point exception (core dumped)
$ clang-3.3 -O3 small.c; a.out
Floating point exception (core dumped)
$ clang-3.2 -O3 small.c; a.out
Floating point exception (core dumped)
$ clang-3.1 -O3 small.c; a.out
Floating point exception (core dumped)
$ clang-3.0 -O3 small.c; a.out
Floating point exception (core dumped)
$ 


--------------------------


int a, c, d, e, f, g;
unsigned int b;

int main ()
{
  for (; c < 1; c++)
    for (; e; e++)
      {
    f = b ? 1 : a / b;
    g = f * e;
    if (g)
      for (;; d++)
        ;
      }

  return 0;
}

-- 
You are receiving this mail because:
You are on the CC list for the bug.
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.llvm.org/pipermail/llvm-bugs/attachments/20130925/9e2dc069/attachment.html>